Method for transmitting resource information for D2D communication and apparatus therefor in wireless communication system

ABSTRACT

Provided is a method for transmitting resource information for device-to-device (D2D) communication of a D2D transmission terminal in a wireless communication system, the method being characterized by comprising the steps of: receiving a resource pool configuration for D2D communication; and transmitting, to a D2D reception terminal, resource information therefor indicating the resource for a first D2D signal transmission to the D2D transmission terminal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2015/007923, filed on Jul. 29, 2015,which claims the benefit of U.S. Provisional Application No. 62/030,565,filed on Jul. 29, 2014, the contents of which are all herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for transmitting resource information fordevice-to-device (D2D) communication in a wireless communication systemand apparatus therefor.

BACKGROUND ART

A 3rd generation partnership project long term evolution (3GPP LTE)(hereinafter, referred to as ‘LTE’) communication system which is anexample of a wireless communication system to which the presentinvention can be applied will be described in brief.

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a wireless communication system. The E-UMTS is an evolved version ofthe conventional UMTS, and its basic standardization is in progressunder the 3rd Generation Partnership Project (3GPP). The E-UMTS may bereferred to as a Long Term Evolution (LTE) system. Details of thetechnical specifications of the UMTS and E-UMTS may be understood withreference to Release 7 and Release 8 of “3rd Generation PartnershipProject; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), basestations (eNode B; eNB), and an Access Gateway (AG) which is located atan end of a network (E-UTRAN) and connected to an external network. Thebase stations may simultaneously transmit multiple data streams for abroadcast service, a multicast service and/or a unicast service.

One or more cells exist for one base station. One cell is set to one ofbandwidths of 1.44, 3, 5, 10, 15 and 20 MHz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to notify the correspondinguser equipment of time and frequency domains to which data will betransmitted and information related to encoding, data size, and hybridautomatic repeat and request (HARQ). Also, the base station transmitsuplink (UL) scheduling information of uplink data to the correspondinguser equipment to notify the corresponding user equipment of time andfrequency domains that can be used by the corresponding user equipment,and information related to encoding, data size, and HARQ. An interfacefor transmitting user traffic or control traffic may be used between thebase stations. A Core Network (CN) may include the AG and a network nodeor the like for user registration of the user equipment. The AG managesmobility of the user equipment on a Tracking Area (TA) basis, whereinone TA includes a plurality of cells.

Although the wireless communication technology developed based on WCDMAhas been evolved into LTE, request and expectation of users andproviders have continued to increase. Also, since another wirelessaccess technology is being continuously developed, new evolution of thewireless communication technology will be required for competitivenessin the future. In this respect, reduction of cost per bit, increase ofavailable service, use of adaptable frequency band, simple structure andopen type interface, proper power consumption of the user equipment,etc. are required.

The UE reports state information of a current channel to the eNBperiodically and/or aperiodically to assist the eNB to efficientlymanage the wireless communication system. Since the reported channelstate information may include results calculated in consideration ofvarious situations and accordingly, a more efficient reporting method isneeded.

DISCLOSURE OF THE INVENTION Technical Task

Based on the above-described discussion, a method for transmittingresource information for device-to-device (D2D) communication in awireless communication system and apparatus therefor are proposed in thepresent invention.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description.

Technical Solutions

In one aspect of the present invention, provided is a method oftransmitting resource information for device-to-device (D2D)communication in a wireless communication system. The method, which isperformed by a D2D transmission user equipment (UE), may include:receiving a resource pool configuration for the D2D communication; andtransmitting, to a D2D reception UE, resource information indicatingresources for first D2D signal transmission from the D2D reception UE tothe D2D transmission UE.

Additionally, when the D2D transmission UE performs the first D2Dtransmission, the resource information may indicate radio resources thatthe D2D transmission UE can receive.

Additionally, the resource information may indicate first radioresources for the first D2D signal transmission. In this case, the firstradio resources may be configured in a resource pool except second radioresources and the second radio resources may be radio resources used forsecond D2D signal transmission from the D2D transmission UE to the D2Dreception UE.

Additionally, the resource information may be mapped to a resource poolfor a scheduling assignment.

Additionally, the resource information may be mapped to a resource poolfor D2D data.

Additionally, the resource information may be transmitted using apredetermined channel and the resources may be determined based on a D2DUE identifier (ID).

Additionally, the resource information may be configured to be cyclicredundancy check (CRC) masked with a D2D UE identifier (ID).

Additionally, the resource information may be configured to include afield associated with identifier (ID) information of the D2Dtransmission UE.

Additionally, the resource information may be configured to betransmitted with control information for either or both of the first D2Dsignal transmission and the second D2D signal transmission.

In another aspect of the present invention, provided is adevice-to-device (D2D) transmission user equipment (UE) for transmittingresource information for D2D communication in a wireless communicationsystem, including a radio frequency unit and a processor. In this case,the processor may be configured to receive a resource pool configurationfor the D2D communication and transmit, to a D2D reception UE, resourceinformation indicating resources for first D2D signal transmission fromthe D2D reception UE to the D2D transmission UE.

Advantageous Effects

According to embodiments of the present invention, resource informationfor D2D communication can efficiently transmitted and received in awireless communication system.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic diagram of an E-UMTS network structure as oneexample of a wireless communication system.

FIG. 2 illustrates structures of control and user planes of a radiointerface protocol between a user equipment and E-UTRAN based on 3GPPradio access network standard.

FIG. 3 illustrates physical channels used in a 3GPP LTE system and ageneral signal transmission method using the same.

FIG. 4 illustrates a structure of a radio frame used in an LTE system.

FIG. 5 illustrates a resource grid for a downlink slot.

FIG. 6 illustrates a structure of a downlink radio frame used in an LTEsystem.

FIG. 7 illustrates a structure of an uplink subframe used in an LTEsystem.

FIG. 8 is a reference diagram for explaining D2D (UE-to-UE)communication.

FIG. 9 illustrates communication performed by a D2D RUE corresponding toan HTX D2D UE according to an embodiment of the present invention.

FIG. 10 illustrates a configuration of a resource unit (RU) for D2Dcommunication.

FIG. 11 illustrates a case in which a scheduling assignment (SA)resource pool and a follow-up data channel resource pool periodicallyappear.

FIG. 12 illustrates a link between an SIG TX UE and an SIG RX UEaccording to the present invention.

FIG. 13 is a reference diagram for explaining a case in which an NSIG RPprecedes an OSIG RP in a time domain according to an embodiment of thepresent invention.

FIG. 14 illustrates a base station and a user equipment applicable toone embodiment of the present invention.

BEST MODE FOR INVENTION

The following technology may be used for various wireless accesstechnologies such as CDMA (code division multiple access), FDMA(frequency division multiple access), TDMA (time division multipleaccess), OFDMA (orthogonal frequency division multiple access), andSC-FDMA (single carrier frequency division multiple access). The CDMAmay be implemented by the radio technology such as UTRA (universalterrestrial radio access) or CDMA2000. The TDMA may be implemented bythe radio technology such as global system for mobile communications(GSM)/general packet radio service (GPRS)/enhanced data rates for GSMevolution (EDGE). The OFDMA may be implemented by the radio technologysuch as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, andevolved UTRA (E-UTRA). The UTRA is a part of a universal mobiletelecommunications system (UMTS). A 3rd generation partnership projectlong term evolution (3GPP LTE) is a part of an evolved UMTS (E-UMTS)that uses E-UTRA, and adopts OFDMA in a downlink and SC-FDMA in anuplink. LTE-advanced (LTE-A) is an evolved version of the 3GPP LTE.

For clarification of the description, although the following embodimentswill be described based on the 3GPP LTE/LTE-A, it is to be understoodthat the technical spirits of the present invention are not limited tothe 3GPP LTE/LTE-A. Also, specific terminologies hereinafter used in theembodiments of the present invention are provided to assistunderstanding of the present invention, and various modifications may bemade in the specific terminologies within the range that they do notdepart from technical spirits of the present invention.

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard. The controlplane means a passageway where control messages are transmitted, whereinthe control messages are used by the user equipment and the network tomanage call. The user plane means a passageway where data generated inan application layer, for example, voice data or Internet packet dataare transmitted.

A physical layer as the first layer provides an information transferservice to an upper layer using a physical channel. The physical layeris connected to a medium access control (MAC) layer via a transportchannel, wherein the medium access control layer is located above thephysical layer. Data are transferred between the medium access controllayer and the physical layer via the transport channel. Data aretransferred between one physical layer of a transmitting side and theother physical layer of a receiving side via the physical channel. Thephysical channel uses time and frequency as radio resources. In moredetail, the physical channel is modulated in accordance with anorthogonal frequency division multiple access (OFDMA) scheme in adownlink, and is modulated in accordance with a single carrier frequencydivision multiple access (SC-FDMA) scheme in an uplink.

A medium access control (MAC) layer of the second layer provides aservice to a radio link control (RLC) layer above the MAC layer via alogical channel. The RLC layer of the second layer supports reliabledata transmission. The RLC layer may be implemented as a functionalblock inside the MAC layer. In order to effectively transmit data usingIP packets such as IPv4 or IPv6 within a radio interface having a narrowbandwidth, a packet data convergence protocol (PDCP) layer of the secondlayer performs header compression to reduce the size of unnecessarycontrol information.

A radio resource control (RRC) layer located on the lowest part of thethird layer is defined in the control plane only. The RRC layer isassociated with configuration, re-configuration and release of radiobearers (‘RBs’) to be in charge of controlling the logical, transportand physical channels. In this case, the RB means a service provided bythe second layer for the data transfer between the user equipment andthe network. To this end, the RRC layers of the user equipment and thenetwork exchange RRC message with each other. If the RRC layer of theuser equipment is RRC connected with the RRC layer of the network, theuser equipment is in an RRC connected mode. If not so, the userequipment is in an RRC idle mode. A non-access stratum (NAS) layerlocated above the RRC layer performs functions such as sessionmanagement and mobility management.

One cell constituting a base station eNB is set to one of bandwidths of1.4, 3.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to several user equipments. At this time, differentcells may be set to provide different bandwidths.

As downlink transport channels carrying data from the network to theuser equipment, there are provided a broadcast channel (BCH) carryingsystem information, a paging channel (PCH) carrying paging message, anda downlink shared channel (SCH) carrying user traffic or controlmessages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted via the downlink SCH or anadditional downlink multicast channel (MCH). Meanwhile, as uplinktransport channels carrying data from the user equipment to the network,there are provided a random access channel (RACH) carrying an initialcontrol message and an uplink shared channel (UL-SCH) carrying usertraffic or control message. As logical channels located above thetransport channels and mapped with the transport channels, there areprovided a broadcast control channel (BCCH), a paging control channel(PCCH), a common control channel (CCCH), a multicast control channel(MCCH), and a multicast traffic channel (MTCH).

FIG. 3 is a diagram illustrating physical channels used in a 3GPP LTEsystem and a general method for transmitting a signal using the physicalchannels.

The user equipment performs initial cell search such as synchronizingwith the base station when it newly enters a cell or the power is turnedon at step S301. To this end, the user equipment synchronizes with thebase station by receiving a primary synchronization channel (P-SCH) anda secondary synchronization channel (S-SCH) from the base station, andacquires information such as cell ID, etc. Afterwards, the userequipment may acquire broadcast information within the cell by receivinga physical broadcast channel (PBCH) from the base station. Meanwhile,the user equipment may identify a downlink channel status by receiving adownlink reference signal (DL RS) at the initial cell search step.

The user equipment which has finished the initial cell search mayacquire more detailed system information by receiving a physicaldownlink shared channel (PDSCH) in accordance with a physical downlinkcontrol channel (PDCCH) and information carried in the PDCCH at stepS302.

Afterwards, the user equipment may perform a random access procedure(RACH) such as steps S303 to S306 to complete access to the basestation. To this end, the user equipment may transmit a preamble througha physical random access channel (PRACH) (S303), and may receive aresponse message to the preamble through the PDCCH and the PDSCHcorresponding to the PDCCH (S304). In case of a contention based RACH,the user equipment may perform a contention resolution procedure such astransmission (S305) of additional physical random access channel andreception (S306) of the physical downlink control channel and thephysical downlink shared channel corresponding to the physical downlinkcontrol channel.

The user equipment which has performed the aforementioned steps mayreceive the physical downlink control channel (PDCCH)/physical downlinkshared channel (PDSCH) (S307) and transmit a physical uplink sharedchannel (PUSCH) and a physical uplink control channel (PUCCH) (S308), asa general procedure of transmitting uplink/downlink signals. Controlinformation transmitted from the user equipment to the base station willbe referred to as uplink control information (UCI). The UCI includesHARQ ACK/NACK (Hybrid Automatic Repeat and reQuestAcknowledgement/Negative-ACK), SR (Scheduling Request), CSI (ChannelState Information), etc. In this specification, the HARQ ACK/NACK willbe referred to as HARQ-ACK or ACK/NACK (A/N). The HARQ-ACK includes atleast one of positive ACK (simply, referred to as ACK), negative ACK(NACK), DTX and NACK/DTX. The CSI includes CQI (Channel QualityIndicator), PMI (Precoding Matrix Indicator), RI (Rank Indication), etc.Although the UCI is generally transmitted through the PUCCH, it may betransmitted through the PUSCH if control information and traffic datashould be transmitted at the same time. Also, the user equipment maynon-periodically transmit the UCI through the PUSCH in accordance withrequest/command of the network.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

Referring to FIG. 4, in a cellular OFDM radio packet communicationsystem, uplink/downlink data packet transmission is performed in a unitof subframe, wherein one subframe is defined by a given time intervalthat includes a plurality of OFDM symbols. The 3GPP LTE standardsupports a type 1 radio frame structure applicable to frequency divisionduplex (FDD) and a type 2 radio frame structure applicable to timedivision duplex (TDD).

FIG. 4(a) is a diagram illustrating a structure of a type 1 radio frame.The downlink radio frame includes 10 subframes, each of which includestwo slots in a time domain. A time required to transmit one subframewill be referred to as a transmission time interval (TTI). For example,one subframe may have a length of lms, and one slot may have a length of0.5 ms. One slot includes a plurality of OFDM symbols in a time domainand a plurality of resource blocks (RB) in a frequency domain. Since the3GPP LTE system uses OFDM in a downlink, OFDM symbols represent onesymbol interval. The OFDM symbol may be referred to as SC-FDMA symbol orsymbol interval. The resource block (RB) as a resource allocation unitmay include a plurality of continuous subcarriers in one slot.

The number of OFDM symbols included in one slot may be varied dependingon configuration of a cyclic prefix (CP). Examples of the CP include anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be 7. If the OFDM symbols are configured by the extended CP,since the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is smaller than that of OFDM symbols incase of the normal CP. For example, in case of the extended CP, thenumber of OFDM symbols included in one slot may be 6. If a channel stateis unstable like the case where the user equipment moves at high speed,the extended CP may be used to reduce inter-symbol interference.

If the normal CP is used, since one slot includes seven OFDM symbols,one subframe includes 14 OFDM symbols. At this time, first maximum threeOFDM symbols of each subframe may be allocated to a physical downlinkcontrol channel (PDCCH), and the other OFDM symbols may be allocated toa physical downlink shared channel (PDSCH).

FIG. 4(b) is a diagram illustrating a structure of a type 2 radio frame.The type 2 radio frame includes two half frames, each of which includesfour general subframes, which include two slots, and a special subframewhich includes a downlink pilot time slot (DwPTS), a guard period (GP),and an uplink pilot time slot (UpPTS).

In the special subframe, the DwPTS is used for initial cell search,synchronization or channel estimation at the user equipment. The UpPTSis used for channel estimation at the base station and uplinktransmission synchronization of the user equipment. In other words, theDwPTS is used for downlink transmission, whereas the UpPTS is used foruplink transmission. Especially, the UpPTS is used for PRACH preamble orSRS transmission. Also, the guard period is to remove interferenceoccurring in the uplink due to multipath delay of downlink signalsbetween the uplink and the downlink.

Configuration of the special subframe is defined in the current 3GPPstandard document as illustrated in Table 1 below. Table 1 illustratesthe DwPTS and the UpPTS in case of T_(s)=1/(15000×2048), and the otherregion is configured for the guard period.

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special subframe Normal cyclic Extended cyclicNormal cyclic Extended cyclic configuration DwPTS prefix in uplinkprefix in uplink DwPTS prefix in uplink prefix in uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — —9 13168 · T_(s) — — —

In the meantime, the structure of the type 2 radio frame, that is,uplink/downlink configuration (UL/DL configuration) in the TDD system isas illustrated in Table 2 below.

TABLE 2 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D DD D D 6 5 ms D S U U U D S U U D

In the above Table 2, D means the downlink subframe, U means the uplinksubframe, and S means the special subframe. Also, Table 2 alsoillustrates a downlink-uplink switching period in the uplink/downlinksubframe configuration of each system.

The structure of the aforementioned radio frame is only exemplary, andvarious modifications may be made in the number of subframes included inthe radio frame, the number of slots included in the subframe, or thenumber of symbols included in the slot.

FIG. 5 illustrates a resource grid for a downlink slot.

Referring to FIG. 5, a DL slot includes N_(symb) ^(DL) OFDM symbols in atime domain and N_(RB) ^(DL) resource blocks in a frequency domain.Since each of the resource blocks includes N_(SC) ^(RB) subcarriers, theDL slot includes N_(RB) ^(DL)×N_(SC) ^(RB) subcarriers in the frequencydomain. Although FIG. 5 shows an example in which the DL slot includes 7OFDM symbols and the resource block includes 12 subcarriers, the presentinvention is not limited thereto. For instance, the number of OFDMsymbols included in the DL slot can vary depending to a length of acyclic prefix (CP).

Each element on a resource grid is referred to as a resource element(RE) and a single resource element is indicated by one OFDM symbol indexand one subcarrier index. A single RB is configured with N_(symb)^(DL)×N_(SC) ^(RB) resource elements. The number (N_(RB) ^(DL)) ofresource blocks included in the DL slot depends on a DL transmissionbandwidth configured in a cell.

FIG. 6 illustrates a structure of a downlink radio frame.

Referring to FIG. 6, up to 3 (or 4) OFDM symbols located at a head partof a first slot of a subframe correspond to a control region to which acontrol channel is assigned. And, the rest of OFDM symbols correspond toa data region to which PDSCH (physical downlink shared channel) isassigned. For example, DL control channels used in the LTE system mayinclude a PCFICH (physical control format indicator channel), a PDCCH(physical downlink control channel), a PHICH (physical hybrid ARQindicator channel) and the like. The PCFICH is transmitted on a firstOFDM symbol of a subframe and carries information on the number of OFDMsymbols in the subframe used for control channel transmission. The PHICHcarries an HARQ ACK/NACK (hybrid automatic repeat requestacknowledgment/negative-acknowledgment) signal in response to ULtransmission.

Control information transmitted on the PDCCH is called DCI (downlinkcontrol information). The DCI includes resource allocation informationand other control information for a user equipment or a user equipmentgroup. For instance, the DCI may include UL/DL scheduling information,UL transmission (Tx) power control command and the like.

The PDCCH carries transmission format and resource allocationinformation of a DL-SCH (downlink shared channel), transmission formatand resource allocation information of a UL-SCH (uplink shared channel),paging information on a PCH (paging channel), system information on aDL-SCH, resource allocation information of a higher-layer controlmessage such as a random access response transmitted on a PDSCH, a Txpower control command set for individual user equipments in a userequipment group, a Tx power control command, activation indicationinformation of a VoIP (voice over IP) and the like. A plurality ofPDCCHs may be transmitted in a control region. A user equipment canmonitor a plurality of PDCCHs. The PDCCH is transmitted on aggregationof one or more consecutive CCEs (control channel elements). In thiscase, the CCE is a logical assignment unit used in providing the PDCCHwith a coding rate based on a radio channel state. The CCE correspondsto a plurality of REGs (resource element groups). The PDCCH format andthe number of PDCCH bits are determined depending on the number of CCEs.A base station determines the PDCCH format in accordance with DCI to betransmitted to a user equipment and attaches CRC (cyclic redundancycheck) to control information. The CRC is masked with an identifier(e.g., RNTI (radio network temporary identifier)) in accordance with anowner or a purpose of use. For instance, if a PDCCH is provided for aspecific user equipment, CRC may be masked with an identifier (e.g.,C-RNTI (cell-RNTI)) of the corresponding user equipment. If a PDCCH isprovided for a paging message, CRC may be masked with a pagingidentifier (e.g., P-RNTI (paging-RNTI)). If a PDCCH is provided forsystem information (particularly, SIC (system information block)), CRCmay be masked with an SI-RNTI (system information-RNTI). In addition, ifa PDCCH is provided for a random access response, CRC may be masked withan RA-RNTI (random access-RNTI).

FIG. 7 illustrates a structure of an uplink subframe used in an LTEsystem.

Referring to FIG. 7, an uplink subframe includes a plurality (e.g., 2slots) of slots. Each of the slots may include a different number ofSC-FDMA symbols depending on a length of CP. The UL subframe may bedivided into a data region and a control region in the frequency domain.The data region includes a PUSCH and is used to transmit such a datasignal as audio and the like. The control region includes a PUCCH and isused to transmit UCI (uplink control information). The PUCCH includes anRB pair located at both ends of the data region on a frequency axis andis hopped on a slot boundary.

The PUCCH can be used to transmit the following control information.

-   -   SR (scheduling request): This is information used to request a        UL-SCH resource and is transmitted using an OOK (on-off keying)        scheme.    -   HARQ ACK/NACK: This is a response signal in response to a DL        data packet on a PDSCH and indicates whether the DL data packet        has been successfully received. 1-bit ACK/NACK is transmitted as        a response to a single downlink codeword and 2-bit ACK/NACK is        transmitted as a response to two downlink codewords.    -   CSI (channel state information): This is feedback information on        a downlink channel. The CSI includes a channel quality indicator        (CQI). MIMO (multiple input multiple output) related feedback        information includes a rank indicator (RI), a precoding matrix        indicator (PMI), a precoding type indicator (PTI) and the like.        20-bit is used in each subframe.

The amount of control information (UCI) that a user equipment cantransmit in a subframe depends on the number of SC-FDMA symbolsavailable for transmission of the control information. The SC-FDMAsymbols available for the transmission of the control informationcorrespond to the rest of SC-FDMA symbols except SC-FDMA symbols usedfor transmitting a reference signal in the subframe. In case of asubframe in which a sounding reference signal (SRS) is configured, thelast SC-FDMA symbol of the subframe is excluded from the SC-FDMA symbolsavailable for the transmission of the control information. The referencesignal is used for coherent detection of a PUCCH.

Hereinafter, D2D (UE-to-UE) communication will be described.

D2D communication schemes can be mainly divided into a scheme supportedby a network/coordination station (e.g., base station) and a scheme notsupported by the network/coordination station.

Referring to FIG. 8, FIG. 8(a) illustrates a scheme in which thenetwork/coordination station intervenes in transmission and reception ofcontrol signals (e.g., grant message), HARQ, channel state information,etc. and user equipments that perform D2D communication transmit andreceive data only. On the other hand, FIG. 8(b) illustrates a scheme inwhich the network provides minimum information (e.g., D2D connectioninformation available in a corresponding cell) only but the userequipments that perform D2D communication establish links and transceivedata.

Based on the above-mentioned discussion, the present invention proposesmethods for enabling a UE that transmits a D2D signal (hereinafterreferred to as “D2D TX UE”) to efficiently transmit various types ofcontrol information to a UE that receives a D2D signal (hereinafterreferred to as “D2D RX UE) when D2D (device-to-device) communication isperformed. Here, the D2D communication means that a UE directlycommunicates with another UE through a radio channel. In addition, thepresent invention can be applied by considering that although the UEmeans a user's terminal, a network entity such as an eNB may also beregarded as the UE if the network entity transmits/receives signalsaccording to a communication method between UEs.

For convenience of description, the present invention is described basedon the 3GPP LTE system. However, the present invention can beextensively applied to other systems as well as the 3GPP LTE system.

As an example of the present invention, a method fordetermining/deciding whether a specific UE is an HTX D2D UE can bedefined as methods 1-A to 1-C below.

Method 1-A: When the amount of data/control information, which needs tobe transmitted, in a (D2D) buffer of a UE is greater than a previouslydefined or signaled threshold value, the UE may be configured todetermine itself as an HTX D2D UE. In this case, the UE that determinesitself as the HTX D2D UE may be configured to report related informationto an eNB through a predefined signal (e.g., physical layer signal orhigher layer signal).

Method 1-B: The eNB may be configured to determine whether a specific UEis an HTX D2D UE through a buffer status report (BSR) information(associated with the amount of existing or newly-defined data/controlinformation that needs to be transmitted) received from thecorresponding specific UE and inform related information through apredefined signal. That is, if the amount of data/control informationthat should be transmitted by the specific UE is equal to or greaterthan a predefined threshold value, the eNB that receives such BSRinformation from the specific UE may determine the correspondingspecific UE as the HTX D2D UE.

Method 1-C: It may be configured that the determination is madeaccording to a type of UE (or a kind of role that is played by the UE).In this case, a type of a specific UE (or a kind of role played by thespecific UE) may be previously defined or signaled. Specifically, UEs inthe examples 1-C-1 to 1-C-3 may be selected as an HTX D2D UE.

Example 1-C-1: A UE configured to (re)transmit information received froma previously defined or signaled UE or eNB to a previously definedsignaled target UE or the eNB (hereinafter referred to as “D2D relay UE(D2D RUE)”).

Example 1-C-2: A UE configured to control/manage D2D group communicationof a UE group (hereinafter referred to as “D2D group owner UE (D2DGOUE)”) (for example, the UE performs transmission of a D2Dsynchronization signal, resource allocation information associated withdata transmission/reception, and the like).

Example 1-C-3: A UE configured to act as an independent synchronizationsource (ISS) (for example, the UE performs transmission of a D2Dsynchronization signal, resource allocation information associated withdata transmission/reception, and the like).

Since the aforementioned HTX D2D UE should or is likely to transmitdata/control information more times than a normal (D2D) UE, the HTX D2DUE needs to efficiently control/manage reception of D2D signals whichare transmitted from different D2D UEs. If the HTX D2D UE is ahalf-duplex (HD) UE and the HTX D2D UE fails to efficientlycontrol/mange the reception of the D2D signals transmitted from thedifferent D2D UEs, transmission operation of the corresponding HTX D2DUE may overlap (or collide) with the reception of the D2D signals fromthe different D2D UEs. In addition, it may cause a problem that the HTXD2D UE fails to receive the corresponding D2D signals successfully(e.g., when the transmission operation has a priority over the receptionoperation) or a problem that the HTX D2D UE fails to transmit its D2Dsignal (e.g., when the reception operation has a priority over thetransmission operation).

FIG. 9 is a reference diagram for explaining an embodiment ofcommunication performed by a D2D RUE (which is selected based on apredetermined rule) corresponding to an HTX D2D UE. FIG. 9 shows a casein which the D2D RUE provides communication connectivity to a D2D UEthat is located out of communication coverage of an eNB or a D2D UE thatcannot directly communicate with the eNB (FIG. 9 (A)) and a case inwhich the D2D RUE provides communication connectivity to a D2D UE thatis located out of communication coverage of a specific D2D UE (e.g., D2DUE#T) or a D2D UE that cannot directly communicate with the D2D UE#T(FIG. 9 (B)).

In this case, the corresponding D2D RUE maintains not only communicationlink (i.e., backhaul link) with the eNB (or the D2D UE#T) but alsocommunication link (i.e., access link) with D2D UE#X and/or D2D UE#Y. Inother words, through the corresponding links, the D2D RUE may forwardinformation received from the eNB (or the D2D UE#T) and information tothe D2D UE#X and/or the D2D UE#Y or forward information received fromthe D2D UE#X and/or the D2D UE#Y to the eNB (or the D2D UE#T).

In addition, the corresponding D2D RUE may have an independent link forD2D communication transmission/reception operation with D2D UE#Z ratherthan relay operation. Since such a D2D RUE (i.e., HTX D2D UE) needs to(re)transmit all information received through access links from aplurality of D2D UEs, the D2D RUE is highly likely to perform (or beperforming) during a relatively long period of time.

In other words, for other D2D UEs (e.g., D2D UE#X, D2D UE#Y, and D2DUE#Z) intending to transmit D2D signals to the D2D RUE (i.e., HTX D2DUE), it is necessary to efficiently share location information ofresources that can be received (or where it is expected that receptionoperation will be performed) by the D2D RUE (e.g., it can mitigate ahalf-duplex problem).

Before describing the particular embodiments of the present invention,resource configuration/allocation when a UE directly communicates withanother UE through a radio channel is described in detail.

In general, when a UE directly communicates with another UE through aradio channel, the UE may select a resource unit (RU) corresponding to aspecific resource in a resource pool corresponding to a set of resourcesand then transmit a D2D signal using the corresponding RU (D2D TX UE'soperation). A D2D RX UE receives resource pool information, which can beused by the D2D TX UE for signal transmission, and then detects thesignal from the D2D TX UE in the corresponding resource pool. In thiscase, the resource pool information may i) be indicated by a basestation when the D2D TX UE is in coverage of the base station or ii) beindicated by another UE or determined as pre-configured resources whenthe D2D TX UE is out of the coverage of the base station.

In general, a resource pool includes a plurality of RUs. In addition,each UE may select one or more RUs to transmit its D2D signal.

FIG. 10 is a reference diagram for explaining an example of a resourceunit (RU) configuration for D2D communication. All frequency resourcesare divided into NF resource units and all time resources are dividedinto NT resource units, thereby defining total (NF*NT) resource units.In this case, the resource pool is repeated with a period of NTsubframes. As shown in FIG. 10, one specific resource unit may berepeated periodically. Alternatively, to obtain a diversity effect in atime dimension or frequency dimension, an index of a physical RU towhich a single logical RU is mapped may be changed according to a timebased on a predetermined pattern. Considering such a resource unitstructure, the resource pool may mean a set of resource units that canbe used by a UE intending to transmit a D2D signal in transmitting theD2D signal.

The aforementioned resource pool can be subdivided into several types.In particular, the resource pool may be classified according to acontent of the D2D signal transmitted in each resource pool. Forexample, the content of the D2D signal can be classified as follows anda separate resource pool may be configured for each content.

-   -   Scheduling assignment (SA): The SA means a signal containing        information such as a location of resources used by each D2D TX        UE for transmitting a follow-up D2D data channel, MCS        (modulation and coding scheme) necessary for demodulation of        other data channels, or a MIMO transmission scheme. In addition,        this signal may be multiplexed and transmitted with D2D data on        the same resource unit. In this case, an SA resource pool may        mean a resource pool where the SA is multiplexed and transmitted        with the D2D data.    -   D2D data channel: The D2D data channel may mean a resource pool        used by the D2D TX UE for transmitting user data by utilizing        the resources designated through the SA. In case the D2D data        channel is multiplexed and transmitted with SA information on        the same resource unit, only the D2D data channel except the SA        information may be transmitted in the resource pool for the D2D        data channel. In other words, resource elements (REs) used for        transmitting the SA information on each resource unit in the SA        resource pool may be used for transmitting the D2D data on the        D2D data channel resource pool.    -   Discovery message: A discovery message resource pool may mean a        resource pool for transmitting the discovery message. The D2D TX        UE may transmit the discovery message containing information        such as its ID for the purpose of enabling neighboring UEs to        discover the corresponding D2D TX UE.

As described above, the D2D resource pool may be classified according tothe content of the D2D signal. However, although D2D signals have thesame content, different resource pools may be used according totransmitting/receiving properties of the D2D signals. For instance, evenin the case of the same D2D data channel or discovery message, differentresource pools may be used according to i) a scheme for determining atransmission timing of a D2D signal (e.g., a scheme for transmitting aD2D signal at a reception time of a synchronization reference signal ora scheme for transmitting a D2D signal at a time obtained by applyingtiming advance to a reception time of a synchronization referencesignal), ii) a scheme for allocating a resource (e.g., a scheme in whichan eNB designates a resource for transmitting each signal for each D2DTX UE or a scheme in which each D2D TX UE autonomously selects aresource for transmitting each signal from its pool), or iii) a signalformat (e.g., the number of symbols occupied by each D2D signal in asingle subframe or the number of subframes used for transmitting asingle D2D signal).

In addition, a resource allocation method for D2D data channeltransmission can be divided into the following two modes.

-   -   Mode 1: In mode 1, an eNB directly designates a resource for        transmitting SA and D2D data for each D2D TX UE. As a result,        the eNB can accurately grasp which UE uses which resource for        D2D signal transmission. However, if the eNB designates a D2D        resource for every D2D signal, it may cause significant        signaling overhead. Hence, the eNB may allocate a plurality of        SA transmission resources and/or data transmission resources        through one-time signaling.    -   Mode 2: In mode 2, each D2D TX UE selects an appropriate        resource from a series of resource pools associated with SA and        data, which are configured by an eNB for a plurality of D2D TX        UEs, and then transmits SA and data. As a result, the eNB cannot        accurately grasp which UE uses which resource for D2D signal        transmission.

FIG. 11 is a reference diagram for explaining a case in which ascheduling assignment (SA) resource pool and a follow-up data channelresource pool periodically appear.

Referring to FIG. 11, the SA resource pool precedes a resource poolcontaining a series of D2D data channels. First, a D2D RX UE attempts SAdetection. Thereafter, if discovering data that the D2D RX UE needs toreceive, the D2D RX UE attempts to receive the data on interconnecteddata resources. Thus, the SA resource pool and the follow-up datachannel resource pool may periodically appear as shown in FIG. 11. Forconvenience of description, a period in which the SA resource poolappears again is hereinafter defined as an SA period.

Hereinafter, a method for efficiently sharing location information ofresources that can be received (or where it is expected that receptionoperation will be performed) by an HTX D2D UE is described. According tothe present invention, an HTX D2D UE is able to efficientlycontrol/manage not only transmission operation but also receptionoperation.

For convenience of description, a UE that transmits informationaccording to the present invention is defined as “SIG TX UE” and a UEthat transmits the information according to the present invention isdefined as “SIG RX UE”.

FIG. 12 is a reference diagram for explaining a link between an SIG TXUE and an SIG RX UE. The SIG TX UE and the SIG RX UE in FIG. 12 can beinterpreted as D2D UEs (e.g., D2D UE#X, D2D UE#Y, and D2D UE#Z in FIG.9) intending to transmit D2D signals to different HTX D2D UEs. Inaddition, a link from the SIG TX UE to the SIG RX UE is defined as“Forward Link (FLink)” and a link from the SIG RX UE to the SIG TX UE isdefined as “Reverse Link (RLink)”.

Information proposed in the present invention (i.e., locationinformation of resources that can be received (or where it is expectedthat reception operation will be performed) by an HTX D2D UE) can bedefined based on the contents/configurations, which will be mentioned inmethods 2-1 to 2-9 below. In the following description, assume that anSIG TX UE is an HTX D2D UE and an SIG RX UE is a D2D UE that intends totransmit a D2D signal to the HTX D2D UE. Further, transmission operationof the HTX D2D UE includes not only signal transmission in an FLinkdirection (e.g., a signal transmitted to the SIG RX UE) but also signal(re)transmission to an eNB (or a specific D2D UE) (e.g., relayoperation).

In addition, in the embodiments of the present invention, the SIG TXUE/HTX D2D UE (or the SIG RX UE) may be configured to transmit aplurality of (previously defined or signaled) SA formats/modified SAformats/other predefined signals/other predefined formats, each of whichincludes control information related with communication in an RLinkdirection and/or the FLink direction, simultaneously (or at one time).

Method 2-1: The SIG TX UE can inform the SIG RX UE of locationinformation of resources to be used for data transmission in the RLinkdirection. Here, the corresponding information transmitted according tothe method 2-1 may indicate i) location information of resources thatcan be received (or where it is expected that reception operation willbe performed) from the perspective of the SIG TX UE or ii) locationinformation of resources where transmission operation will not beperformed (or where it is expected that the transmission operation willnot be performed) from the perspective of the SIG TX UE. Moreover,although the information transmission operation according to the method2-1 is performed in the FLink direction, resource location informationassociated with the data transmission in the RLink direction can also beinformed.

Furthermore, the corresponding information according to the method 2-1may inform the SIG RX UE of only indices (e.g., T-RPT (time resourcepattern or time resource pattern of transmission)) of time resourceswhere the SIG TX UE performs the reception operation. Alternatively, theinformation may inform the SIG RX UE of only indices (e.g., T-RPT) oftime resources where the SIG TX UE does not perform the transmissionoperation.

Method 2-2: The SIG TX UE can inform the SIG RX UE of locationinformation of resources to be used by the SIG TX UE for thetransmission operation. Here, the information according to the method2-2 may indicate i) location information of resources where it isexpected that the transmission operation will be performed (or where thetransmission operation will be performed) from the perspective of theSIG TX UE or ii) location information of resources where receptionoperation associated with the RLink will not be performed (or where itis expected that the reception operation associated with the RLink willnot be performed) from the perspective of the SIG TX UE.

In addition, the corresponding information according to the method 2-2may also inform the SIG RX UE of only indices (e.g., T-RPT) of timeresources where the transmission operation will be performed (or whereit is expected that the transmission operation will be performed) by theSIG TX UE. After receiving such information, the SIG RX UE may use theremaining time resources as much as possible except the time resourceswhere the SIG TX UE performs the transmission operation whentransmitting D2D data to the SIG TX UE. Thus, the SIG TX UE can receivedata on resources as much as possible. If some of resources that aredetermined by the SIG RX UE to be used for D2D data transmission isincluded in transmission resources of the SIG TX UE, it is possible toskip D2D data transmission on the corresponding resources. The reasonfor this is to reduce interference caused by unnecessary transmissionbecause the SIG TX UE may not perform reception operation on thecorresponding resources.

The information mentioned in the methods 2-1 and 2-2 may betransmitted/received (or exchanged) in the form of a signal to which thefollowing methods 2-3 to 2-5 are applied. Here, fields/contents thereofaccording to the methods 2-3 to 2-5 may be extensively appliedtherebetween.

Method 2-3: According to the method 2-3, signals can betransmitted/received through the conventional SA format or a formatmodified therefrom.

Example 2-3-1: Even if there is no follow-up data transmission, theconventional SA format or format modified therefrom that carriesinformation according to the method 2-3 can be independently transmitted(i.e., SA only transmission can be performed).

Example 2-3-2: When the SIG TX UE informs the SIG RX UE of only indices(e.g., T-RPT) of time resources where the transmission/receptionoperation will be performed according to the aforementioned methods 2-1and 2-2, a field/bit for indicating frequency resource locationinformation in the conventional SA format may be unnecessary. In thiscase, such an extra field/bit may be configured to be used (merged) toinform locations of the time resources where the transmission/receptionoperation will be performed by the SIG TX UE (i.e., it is possible toincrease the number of T-RPT candidates).

Example 2-3-3: The location information of the resources where the SIGTX UE will perform the transmission operation and the locationinformation of the resources to be used for the data transmission in theRLink direction may be simultaneously informed through one time of SAformat transmission (e.g., as unicast operation). In this case, forexample, in an T-RPT designated by an SA, odd-numbered resources may beused for the SIG TX UE's transmission operation and even-numberedresources may be used for the SIG TX UE's data reception in the RLinkdirection based on a predefined rule/signaling.

Example 2-3-4: By defining an additional field an additional field(e.g., 1-bit tag field) on the conventional SA format, it is possible todistinguish whether time resource location information and/or frequencyresource location information of the corresponding modified SA format(i.e., the conventional SA format+the additional field) is i) thelocation information of the resources to be used for the datatransmission in the RLink direction or ii) the location information ofthe resources where the SIG TX UE will perform the transmissionoperation.

Example 2-3-5: The conventional SA format or format modified therefrommay be i) signaled in a dedicated manner, i.e., a designated specificresource may be informed a specific UE or ii) be signaled in abroadcasting manner, i.e., information on an RLink/FLink resource poolmay be informed a plurality of unspecific UEs (or a UE group) (e.g., theSIG TX UE may signal a subset of a D2D resource pool, which is signaledfrom an eNB (or a specific D2D UE) or previously defined, as itsreception-available resource pool (e.g., T-RPT)).

Method 2-4: According to the method 2-4, signals can betransmitted/received using a D2D data channel.

Example 2-4-1: The SIG TX UE may also inform the SIG RX UE of thelocation information of the resources where the SIG TX UE will performthe transmission/reception operation through a (previously defined orsignaled) D2D data channel (instead of using the SA format). Here, sucha D2D data channel may be used i) in a dedicated manner, i.e., adesignated specific resource may be informed a specific UE or ii) in abroadcasting manner, i.e., information on an RLink/FLink resource poolmay be informed a plurality of unspecific UEs (or a UE group).

As an example of the broadcasting (i.e., the latter one), the SIG TX UEmay broadcast a subset of a resource pool associated with D2D signaltransmission/reception, which is broadcasted from an eNB (or a specificD2D UE) or previously defined, as its reception-available resource pool(e.g., the method 2-1). As another example, the SIG TX UE may broadcasta subset of the resource pool associated with D2D signaltransmission/reception, which is broadcasted from the eNB (or thespecific D2D UE) or previously defined, as a resource pool where itstransmission operation is performed (e.g., the method 2-2). Further,such operation may be performed through a previously defined or signaledbroadcast data channel.

Example 2-4-2: Such a D2D channel may be independently transmitted(without preceding SA format transmission) (i.e., D2D data channel onlytransmission). In the example 2-4-2, resources used for transmitting thecorresponding D2D data channel may i) be defined or signaled in advance,ii) be determined based on a function having a new UE ID, which ispreviously defined or signaled, as an input variable, or iii) bedetermined based on a function having a physical layer ID/cell ID, whichis generated from a UE ID, as an input variable.

Method 2-5: According to the method 2-5, signals may betransmitted/received through a newly defined channel (hereinafter named“special channel (SChannel)”)

Example 2-5-1: The SChannel may be introduced to for the informationtransmission according to the method 2-5. Here, the SChannel may bedefined to have fields/contents similar to those of the conventional SAformat or format modified therefrom mentioned in the method 2-3 or thoseof the D2D data channel mentioned in the method 2-4. In addition,resources for transmitting the SChannel according to the method 2-5 mayi) be defined or signaled in advance, ii) be determined based on afunction having a new UE ID, which is previously defined or signaled, asan input variable, or iii) be determined based on a function having aphysical layer ID/cell ID, which is generated from a UE ID, as an inputvariable.

The signal (e.g., method 2-3, method 2-4, or method 2-5) carrying theinformation (e.g., method 2-1 or method 2-2) described in the presentinvention may be distinguished from the conventional SA format and/orthe D2D data channel (which are associated with the FLink) based on thefollowing methods 2-6 to 2-9.

Method 2-6: Unlike the conventional SA format associated with the FLink,the signal carrying the information according to the present inventionmay be configured such that i) CRC masking/decoding is performed thereonbased on a new UE ID that is previously signaled or defined or aphysical layer ID value generated from a UE ID or ii) scrambling/basesequence group hopping/sequence hopping is performed thereon based on apreviously signaled or defined cell ID.

Method 2-7: Unlike the configuration of the conventional SA formatassociated with the FLink, in the signal carrying the informationaccording to the present invention, a field associated with transmissionof SIG TX UE's ID information may be defined i) with or ii) without afield associated with transmission of SIG RX UE's ID information. Inaddition, to distinguish a signal for carrying information according tothe method 2-7 from the conventional SA format (and/or the D2D datachannel), an indicator field for indicating the signal may be defined.

Method 2-8: A resource pool where the signal carrying the informationaccording to the present invention is transmitted (hereinafter named“new signal resource pool (NSIG RP)”) and a resource pool where theconventional signal (e.g., the conventional SA format and/or the D2Ddata channel) is transmitted (hereinafter named as “original signalresource pool (OSIG RP)”) may be independently configured (e.g., atleast parts (i.e., some or all) of them are different from the another).In this case, the NSIG RP may be configured to precede the OSIG RP (inthe time domain) or periodically appear at a (previously defined orsignaled) independent period.

FIG. 13 is a reference diagram for explaining a case in which the NSIGRP precedes the OSIG RP in the time domain as described in the method2-8 of the present invention.

In such a case (shown in FIG. 13), a D2D UE (i.e., an SIG RX UE) thatintends to transmit a D2D signal (e.g., data in the RLink direction) toan HTX D2D UE (i.e., an SIG TX UE) may be configured to preferentiallyperform search/blind detection for/of a signal, which carriesinformation according to the method 2-8, transmitted from the HTX D2D UEon the NSIG RP.

After performing a procedure for the search/blind detection, thecorresponding D2D UE may perform D2D signal transmission operation inthe RLink direction using other resources rather than resources used bythe HTX D2D UE for transmission (or resources to be used by the HTX D2DUE for reception operation). An SA format including relevant information(i.e., resource allocation information associated with the D2D signaltransmission operation in the RLink direction) is transmitted on theOSIG RP.

According to the procedures described with reference to the method 2-8,the D2D UE intending to transmit a D2D signal to the HTX D2D UE cansuccessfully transmit the corresponding D2D signal (with a highprobability). In addition, it is also possible to a problem caused byhalf-duplex characteristics.

In this case, only the D2D UE intending to transmit a D2D signal to theHTX D2D UE may be configured to additionally perform the search/blinddetection for/of the signal, which carries the information according tothe method 2-8, transmitted from the HTX D2D UE on the NSIG RP. On theother hand, a D2D UE intending to transmit a D2D signal to a normal D2DUE (i.e., non-HTX D2D UE) may be configured to perform search/blinddetection for/of the conventional SA format on only the OSIG RP.

Method 2-9:

According to the method 2-9, the NSIG RP where the signal carrying theinformation according to the present invention is transmitted and theOSIG RP where the conventional signal (e.g., the conventional SA formatand/or the D2D data channel) is transmitted may be defined as the sameresource pool. In other words, the signal carrying the informationaccording to the present invention may be transmitted by beingmultiplexed with the conventional signal (e.g., the conventional SAformat and/or the D2D data channel) in the same resource pool.

Each of the aforementioned embodiments/configurations/rules of thepresent invention can be interpreted/applied/implemented as anindependent embodiment. And, it is possible to implement each of theaforementioned embodiments not only independently but also by combining(or merging) at least one of the embodiments.

In addition, in this specification, the term such as “D2D(device-to-device) communication” can be interpreted as “V2X(vehicle-to-X) communication”. Here, for example, “X” may be interpretedas a vehicle (i.e., V2V), a person (i.e., V2P), an infra-structure(i.e., V2I), or the like.

Moreover, the aforementioned embodiments of the present invention may beconfigured to be limitedly applied only to Mode 1 (or Mode 2) D2Dcommunication. Furthermore, the aforementioned embodiments of thepresent invention may be configured to be limitedly applied only to D2Dcommunication operation and/or D2D discovery operation. Further, theaforementioned embodiments of the present invention may be configured tobe limitedly applied only to V2X communication.

Further, the aforementioned embodiments of the present invention may beapplied to a case in which an SIG TX UE informs an SIG RX UE of variouscontrol information associated with data to be transmitted from the SIGRX UE to another D2D UE (rather than the SIG TX UE).

Further, the aforementioned embodiments of the present invention may beapplied to a case in which when D2D communication is extended in theform of unicast, a D2D TX UE (or an SIG TX UE) informs a D2D RX UE (oran SIG RX UE) of various types of control information besides controlinformation on transmission data.

Further, the embodiments of the present invention can also be applied tothe following case. In case D2D operation is performed on an unlicensedband, if an SIG TX UE determines that a channel is idle due to notransmission from neighboring devices, the SIG TX UE may designate RLinkresources by transmitting a signal containing the information accordingto the present invention. Thereafter, the SIG RX UE may transmit datausing the corresponding resources.

Further, the aforementioned embodiments of the present invention can beextensively applied to a case in which when D2D communication isperformed on an unlicensed band, an SIG RX UE informs an SIG TX UE of acarrier sensing result performed on the unlicensed band (e.g.,BUSY/IDLE) and/or resource allocation/control information associatedwith data transmission in the FLink direction.

Further, although the above embodiments are mainly described on theassumption that transmission is performed in the FLink direction, theembodiments can be used to inform an SIG RX UE of various controlinformation associated with signal transmission in the RLink directionand/or various control information associated with signal transmissionin the FLink direction. Particular examples will be described withreference to usage #1 to usage #7. Further, in the signal according tothe present invention, a field for indicating usage (e.g., “(usage #1)to (usage #7) or (method 2-1) to (method 2-2)”) of the correspondingsignal may be defined. Alternatively, the signal may include anindicator indicating usage of the corresponding signal.

Control Information Associated with Communication in RLink Direction

Usage #1: According to the present invention, an indicator fortriggering transmission of TA (timing advance) information associatedwith communication in the RLink direction can be transmitted. Thecorresponding indicator associated with the usage #1 may be used by theSIG TX UE to (re)transmit, to the SIG RX UE, TA information associatedwith D2D signal reception in the RLink direction. In this case, thetransmission of the indicator may be interpreted as that since it isdetermined (from the perspective of the SIG TX UE) that RLink-relatedtime synchronization is inaccurate, the SIG RX UE is requested to(re)adjust/update (current) RLink-related TA information.

Usage #2: According to the present invention, TPC (transmission powercontrol) information associated with D2D signal transmission in theRLink direction can be transmitted. The information associated withusage #2 may be transmitted through a TPC field defined in the signalaccording to the present invention and the corresponding TPC field maycarry a previously configured or signaled offset value for (current) D2Dsignal transmission power in the RLink direction. The above-mentionedoperation may be performed according to an absolute power control method(or an accumulated power control method). Moreover, the correspondingTPC field may also be used to indicate previously configured or signaledincrease/decrease in the (current) D2D signal transmission power in theRLink direction.

As another example, a plurality of (previously defined or signaled) TPCfields may be defined in the signal according to the present invention(e.g., similar to DCI format 3/3A). In this case, a TPC field may beinterconnected to previously defined or signaled specific RLink andcarry control information for (current) D2D signal transmission power ina direction toward the corresponding specific RLink. In other words,when the above-mentioned scheme associated with the usage #2 is applied,the signal according to the present invention may carry power controlinformation associated with a plurality of RLinks.

Control Information Associated with Communication in FLink Direction

Usage #3: According to the present invention, TA information associatedwith communication in the FLink direction can be transmitted. Thecorresponding TA information may be used by the SIG TX UE to inform theSIG RX UE of TA information associated with D2D signal reception in theFLink direction. In this case, transmission of the TA informationassociated with the usage #3 can be performed as shown in examples #3-1to #3-3. In addition, such a signal may indicate that the TA informationassociated with the D2D signal reception in the FLink direction (or anSA to be applied to the FLink) is updated (by the SA TX UE). Moreover,the following examples #3-1 to #3-3 can be extensively applied totransmission of the TA information associated with D2D signal receptionin the RLink direction (e.g., the usage #1).

Example #3-1: If the SIG TX UE transmits signals based on a proposedscheme in which a TA information related field (e.g., T bits) is definedseveral times (as many as a previously defined or signaled number oftimes), the TA information associated with the D2D signal reception inthe FLink direction may be configured in a relatively accurate manner(i.e., it may be interpreted as gradual adjustment).

Specifically, if the signal having the TA field defined thereinaccording to the present invention is transmitted N times (e.g.,“transmission of a first signal including TA1 information, transmissionof a second signal including TA2 information, . . . , and transmissionof an N^(th) signal including TAN information”), the SIG RX UE mayassume that a value of “TA1+TA2+ . . . +TAN” is a final TA for the D2Dsignal reception in the FLink direction after receiving thecorresponding N signals.

In this case, it may be defined/configured that N times of SA formattransmission is performed on a single (identical) resource pool or aplurality of resource pools. For instance, in the latter case (i.e.,when SA formats are transmitted in a plurality of resource pools), itmay mitigate a problem caused by HD (half-duplex) characteristics, i.e.,a case in which the SA RX UE fails to receive the corresponding (some orall of N) SA formats due to transmission of a D2D signal (e.g.,discovery message, D2D data channel, SA, etc.).

Example #3-2: In the signal described in the example #3-1 of the presentinvention, a granularity indicator field (GIF) associated with TAinformation may be defined. In this case, the GIF indicates anincrease/decrease interval of a TA value indicated by a TA field.

As a particular example, if a TA field is set to ‘0000010’ and a GIFindicates a K value, the SIG RX UE may assume that a value of “apreviously defined or signaled reference value (e.g., 0)+2*K value” isthe final TA for the D2D signal reception in the FLink direction.

In this case, it can be defined that a value indicated by a specific bitof the GIF may be i) signaled from an eNB, ii) fixed to a specific valuein the specification, or iii) determined as a value interconnected to aresource pool associated with D2D signal transmis sion/reception.

The GIF may indicate at least (some or all) different values in eachsignal transmission according to the present invention. Specifically, inthe N times of the signal transmission, the GIF may represent arelatively large value (i.e., coarse TA adjustment) in preceding M timesof the signal transmission. On the contrary, in the following (N-M)times of the signal transmission, the GIF may represent a relativelysmall value (i.e., fine TA adjustment). The purpose of the above methodis to configure a relatively accurate TA value within the N times of thesignal transmission.

As a further example, instead of defining the aforementioned GIF, a TAfield may have at least (some or all) different sizes in each signaltransmission according to the present invention in order to configurethe relatively accurate TA value. Specifically, in the N times of thesignal transmission, TA field sizes may be set to be relatively small inpreceding M times of the signal transmission. On the contrary, in thefollowing (N-M) times of the signal transmission, TA field sizes may beset to be relatively large. For instance, the small TA field sizes(e.g., S bits) may be interpreted as that a predefined range of TAvalues (i.e., “from TA_MIN to TA_MAX”) is divided into a relativelysmall numeral (e.g., 2^(S)) (i.e., coarse TA adjustment). On the otherhand, the large TA field sizes (e.g., L bits (L>S)) may be interpretedas that the predefined range of TA values is divided into a relativelylarge numeral (e.g., 2^(L)) (i.e., fine TA adjustment). As a furtherexample, although the same (previously defined or signaled) TAgranularity value is assumed in the N times of the signal transmission,the TA field may (still) have at least (some or all) different sizes ineach signal transmission. For instance, in case of a small TA fieldsize, since the number of TA values (candidates) that can be indicatedby the corresponding field is decreased, it is possible to apply coarseTA adjustment operation. On the other hand, in case of a large TA fieldsize, since the number of TA values (candidates) that can be indicatedby the corresponding field is increased, it is possible to apply fine TAadjustment operation. As a further example, instead ofdefining/configuring the GIF additionally or changing the TA fieldsizes, it may be configured that at least (some or all) different TAgranularity values, which are defined or signaled in advance, areapplied according to an order of the signal transmission according tothe present invention.

Example #3-3: In the signal described in the example #3-1 of the presentinvention, an order indication field (OIF) indicating how many signalsare transmitted before a signal transmitted at a specific time (amongthe previously defined or signaled N signals) may be defined. Forinstance, If the SIG RX UE recognizes that it fails to receive at leastone of the N signals, the SIG RX UE may be configured to i) inform theSIG TX UE of the failure through a predefined signal (for example, afterreceiving the corresponding feedback signal, the SIG TX UE mayretransmit TA information associated with the signal which the SIG RX UEfails to receive), ii) apply a specific final TA value which ispreviously defined or signaled, or iii) assume TA information associatedwith the signal which the SA RX UE fails to receive to be a previouslydefined or signaled specific value.

In addition, instead of defining the OIF separately, how many signalsare transmitted before the signal transmitted at the specific time(among the previously defined or signaled N signals) may be graspedbased on a location of a time and/or frequency resource where thecorresponding signal is transmitted or a resource type (e.g., CS, OCC,antenna port, etc.) of a reference signal (e.g., DM-RS) used fortransmitting/decoding the corresponding signal.

Usage #4: According to the present invention, TPC information associatedwith D2D signal transmission in the FLink direction can be transmitted.In this case, the corresponding information may be transmitted through aTPC field defined in the signal according to the present invention andthe corresponding TPC field may be used for informing a (previouslydetermined or signaled) offset value for (current) D2D signaltransmission power in the FLink direction. The above-mentioned operationmay be performed according to an absolute power control method (or anaccumulated power control method).

Moreover, a plurality of (previously defined or signaled) TPC fields maybe defined in a single signal (e.g., similar to DCI format 3/3A). Inthis case, a TPC field may be interconnected to previously defined orsignaled specific FLink and carry control information for (current) D2Dsignal transmission power in a direction toward the correspondingspecific FLink. In other words, when the above-mentioned schemeassociated with the usage #4 is applied, the single signal may carrypower control information associated with a plurality of FLinks.

Usage #5: According to the present invention, wake-up indicationinformation for the D2D signal reception in the FLink direction can betransmitted. The indication information for usage #5 may be used by theSIG TX UE to enable its target UE (or the SIG RX UE) to perform the D2Dsignal reception in the FLink direction by waking up the target UE. Thisinformation may be used for the purpose of paging associated with D2Dcommunication. In addition, such a method can be extensively applied toa case in which the SIG RX UE enables its target UE (or the SIG TX UE)to perform the D2D signal reception in the RLink direction by waking upthe target UE.

Usage #6: According to the present invention, an indicator fortriggering CSI measurement operation and/or CSI reporting operation canbe transmitted. For instance, the indicator associated with usage #6 maybe used by the SIG TX UE to instruct its target UE (or the SIG RX UE) toperform the CSI measurement operation and/or the CSI reporting operationwith respect to links between the corresponding UEs. In this case, forinstance, it may be configured that the corresponding CSI measurementoperation is performed based on DM-RSs used in signaltransmission/decoding according to the present invention. The measuredCSI may be transmitted through the RLink using an RPT (time resourcepattern or resource pattern of transmission) indicated by thecorresponding signal. In addition, such a method may be extensivelyapplied to the RLink direction (e.g., transmission from the SIG RX UE toits target UE (or the SIG TX UE)).

Usage #7: According to the present invention, some (RLink/FLink-related)information indicated through a PDCCH (e.g., DM-RS CS, NDI, MCS/RV, FH,HARQ ID, PMI, etc.) may be configured to be informed.

Each of the aforementioned embodiments/configurations/rules of thepresent invention can be interpreted/applied/implemented as oneindependent embodiment. And, it is possible to implement each of theaforementioned embodiments not only independently but also by combining(or merging) at least one of the embodiments.

Moreover, the aforementioned embodiments of the present invention may beconfigured to be limitedly applied only to Mode 1 D2D communication orMode 2 D2D communication.

Furthermore, the aforementioned embodiments of the present invention maybe configured to be limitedly applied only to D2D communication or onlywhen D2D discovery is performed

Further, the aforementioned embodiment (e.g., SA only transmission) ofthe present invention can be extensively applied to i) a case in whichwhen D2D communication is performed on an unlicensed band, a D2D RX UEinforms a D2D TX UE of a carrier sensing result performed on theunlicensed band (e.g., BUSY/IDLE) or ii) a case in which resourceallocation/control information associated with data transmission in theFLink direction is informed.

Further, the embodiments of the present invention can be extensivelyapplied when an HTX (heavy transmission) D2D UE (e.g., D2D relay UE (D2DRUE), D2D group owner UE (D2D GOUE), independent synchronization source(ISSS), etc.) shares location information of resources that can bereceived (or where it is expected that reception operation will beperformed).

FIG. 14 is a diagram of a base station and a user equipment applicableto one embodiment of the present invention.

If a relay node is included in a wireless communication system,communication in a backhaul link is performed between a base station andthe relay node and communication in an access link is performed betweenthe relay node and a user equipment. Therefore, the base station or userequipment shown in the drawing can be substituted with the relay node insome cases.

Referring to FIG. 14, a wireless communication system includes a basestation (BS) 110 and a user equipment (UE) 120. The base station 110includes a processor 112, a memory 114 and an RF (radio frequency) unit116. The processor 112 can be configured to implement the proceduresand/or methods proposed in the present invention. The memory 114 isconnected to the processor 112 and stores various kinds of informationrelated to operations of the processor 112. The RF unit 116 is connectedto the processor 112 and transmits and/or receives radio or wirelesssignals. The user equipment 120 includes a processor 122, a memory 124and an RF unit 126. The processor 122 can be configured to implement theprocedures and/or methods proposed in the present invention. The memory124 is connected to the processor 122 and stores various kinds ofinformation related to operations of the processor 122. The RF unit 126is connected to the processor 122 and transmits and/or receives radio orwireless signals. The base station 110 and/or the user equipment 120 canhave a single antenna or multiple antennas.

The above-described embodiments may correspond to combinations ofelements and features of the present invention in prescribed forms. And,it may be able to consider that the respective elements or features maybe selective unless they are explicitly mentioned. Each of the elementsor features may be implemented in a form failing to be combined withother elements or features. Moreover, it may be able to implement anembodiment of the present invention by combining elements and/orfeatures together in part. A sequence of operations explained for eachembodiment of the present invention may be modified. Some configurationsor features of one embodiment may be included in another embodiment orcan be substituted for corresponding configurations or features ofanother embodiment. And, it is apparently understandable that a newembodiment may be configured by combining claims failing to haverelation of explicit citation in the appended claims together or may beincluded as new claims by amendment after filing an application.

In this disclosure, a specific operation explained as performed by abase station can be performed by an upper node of the base station insome cases. In particular, in a network constructed with a plurality ofnetwork nodes including a base station, it is apparent that variousoperations performed for communication with a user equipment can beperformed by a base station or other network nodes except the basestation. In this case, ‘base station’ can be replaced by such aterminology as a fixed station, a Node B, an eNodeB (eNB), an accesspoint and the like.

The embodiments of the present invention may be implemented usingvarious means. For instance, the embodiments of the present inventionmay be implemented using hardware, firmware, software and/or anycombinations thereof. In case of the implementation by hardware, oneembodiment of the present invention may be implemented by at least oneof ASICs (application specific integrated circuits), DSPs (digitalsignal processors), DSPDs (digital signal processing devices), PLDs(programmable logic devices), FPGAs (field programmable gate arrays),processor, controller, microcontroller, microprocessor and the like.

In case of the implementation by firmware or software, one embodiment ofthe present invention may be implemented by modules, procedures, and/orfunctions for performing the above-explained functions or operations.Software code may be stored in a memory unit and may be then driven by aprocessor.

The memory unit may be provided within or outside the processor toexchange data with the processor through the various means known to thepublic.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

INDUSTRIAL APPLICABILITY

Although a method for transmitting resource information fordevice-to-device (D2D) communication in a wireless communication systemand apparatus therefor are mainly described with reference to examplesapplied to a 3GPP LTE system, the method and apparatus can be applied tovarious kinds of wireless communication systems as well as the 3GPP LTEsystem.

What is claimed is:
 1. A method of transmitting resource information fordevice-to-device (D2D) communication in a wireless communication system,the method performed by a D2D transmission user equipment (UE) andcomprising: receiving a resource pool configuration for the D2Dcommunication; transmitting, to a D2D reception UE, resource informationincluding a time resource pattern (T-RPT) indicating resources for afirst D2D signal transmission from the D2D reception UE to the D2Dtransmission UE; and configuring to determine the D2D transmission UE asa heavy transmission (HTX) D2D UE when an amount of information to betransmitted by the D2D transmission UE is greater than a thresholdvalue, wherein if the D2D transmission UE is not determined as the HTXD2D UE, resources indicated by the T-RPT are used for D2D signaltransmission, wherein if the D2D transmission UE is determined as theHTX D2D UE, odd-numbered resources indicated by the T-RPT are used forD2D signal transmission, and even-numbered resources indicated by theT-RPT are used for D2D signal reception, wherein the resourceinformation indicates first radio resources for the first D2D signaltransmission, wherein the first radio resources are configured in aresource pool excluding second radio resources, and wherein the secondradio resources are radio resources used for a second D2D signaltransmission from the D2D transmission UE to the D2D reception UE. 2.The method of claim 1, wherein, when the D2D transmission UE performsthe first D2D transmission, the resource information indicates radioresources that the D2D transmission UE can receive.
 3. The method ofclaim 1, wherein the resource information is mapped to a resource poolfor D2D data.
 4. The method of claim 1, wherein the resource informationis transmitted using a predetermined channel and wherein the resourcesare determined based on a D2D UE identifier (ID).
 5. The method of claim1, wherein the resource information is configured to be cyclicredundancy check (CRC) masked with a D2D UE identifier (ID).
 6. Themethod of claim 1, wherein the resource information is configured toinclude a field associated with identifier (ID) information of the D2Dtransmission UE.
 7. The method of claim 1, wherein the resourceinformation is configured to be transmitted with control information foreither or both of the first D2D signal transmission and a second D2Dsignal transmission from the D2D transmission UE to the D2D receptionUE.
 8. A device-to-device (D2D) transmission user equipment (UE) fortransmitting resource information for D2D communication in a wirelesscommunication system, the D2D transmission UE comprising: a transmitterand a receiver; and a processor, wherein the processor is configured to:receive a resource pool configuration for the D2D communication;transmit, to a D2D reception UE, resource information including a timeresource pattern (T-RPT) indicating resources for a first D2D signaltransmission from the D2D reception UE to the D2D transmission UE; andconfigure to determine the D2D transmission UE as a heavy transmission(HTX) D2D UE when an amount of information to be transmitted by the D2Dtransmission UE is greater than a threshold value, wherein if the D2Dtransmission UE is not determined as the HTX D2D UE, resources indicatedby the T-RPT are used for D2D signal transmission, wherein if the D2Dtransmission UE is determined as the HTX D2D UE, odd-numbered resourcesindicated by the T-RPT are used for D2D signal transmission, andeven-numbered resources indicated by the T-RPT are used for D2D signalreception, wherein the resource information indicates first radioresources for the first D2D signal transmission, wherein the first radioresources are configured in a resource pool excluding second radioresources, and wherein the second radio resources are radio resourcesused for a second D2D signal transmission from the D2D transmission UEto the D2D reception UE.